# Inspired by: https://github.com/huggingface/transformers/blob/v4.29.2/examples/pytorch/language-modeling/run_clm.py

import math
from typing import Optional, List
from transformers import Seq2SeqTrainingArguments, DataCollatorForSeq2Seq, TrainerCallback

from llmtuner.dsets import get_dataset, preprocess_dataset
from llmtuner.extras.callbacks import LogCallback
from llmtuner.extras.constants import IGNORE_INDEX
from llmtuner.extras.ploting import plot_loss
from llmtuner.hparams import ModelArguments, DataArguments, FinetuningArguments
from llmtuner.tuner.core import load_model_and_tokenizer
from llmtuner.tuner.core.trainer import PeftTrainer


def run_pt(
    model_args: ModelArguments,
    data_args: DataArguments,
    training_args: Seq2SeqTrainingArguments,
    finetuning_args: FinetuningArguments,
    callbacks: Optional[List[TrainerCallback]] = [LogCallback()]
):
    dataset = get_dataset(model_args, data_args)
    model, tokenizer = load_model_and_tokenizer(model_args, finetuning_args, training_args.do_train, stage="pt")
    dataset = preprocess_dataset(dataset, tokenizer, data_args, training_args, stage="pt")
    data_collator = DataCollatorForSeq2Seq(
        tokenizer=tokenizer,
        label_pad_token_id=IGNORE_INDEX if data_args.ignore_pad_token_for_loss else tokenizer.pad_token_id
    )

    # Split the dataset
    if training_args.do_train:
        if data_args.dev_ratio > 1e-6:
            dataset = dataset.train_test_split(test_size=data_args.dev_ratio)
            trainer_kwargs = {"train_dataset": dataset["train"], "eval_dataset": dataset["test"]}
        else:
            trainer_kwargs = {"train_dataset": dataset}
    else: # do_eval or do_predict
        trainer_kwargs = {"eval_dataset": dataset}

    # Initialize our Trainer
    trainer = PeftTrainer(
        finetuning_args=finetuning_args,
        model=model,
        args=training_args,
        tokenizer=tokenizer,
        data_collator=data_collator,
        callbacks=callbacks,
        **trainer_kwargs
    )

    # Training
    if training_args.do_train:
        train_result = trainer.train()
        trainer.log_metrics("train", train_result.metrics)
        trainer.save_metrics("train", train_result.metrics)
        trainer.save_state()
        trainer.save_model()
        if trainer.is_world_process_zero() and model_args.plot_loss:
            plot_loss(training_args.output_dir, keys=["loss", "eval_loss"])

    # Evaluation
    if training_args.do_eval:
        metrics = trainer.evaluate(metric_key_prefix="eval")
        try:
            perplexity = math.exp(metrics["eval_loss"])
        except OverflowError:
            perplexity = float("inf")

        metrics["perplexity"] = perplexity

        trainer.log_metrics("eval", metrics)
        trainer.save_metrics("eval", metrics)